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May 2008

Fact Sheet

KEY FACTS ABOUT APPLYING LARVICIDES TO CATCH BASINS AND STAGNANT WATER LOCATED ON PRIVATE PROPERTY

What is a larvicide?

Mosquitoes have a four-stage life cycle: egg, larva, pupa and adult. A larvicide is a pesticide that kills the larvae directly before they mature. Larvicides are placed in stagnant water which is where mosquitoes prefer to lay their eggs for the larvae to hatch (e.g., catch basins or storm sewers). Larviciding reduces the adult mosquito populations that have the ability to act as carriers of the West Nile Virus.

What is a catch basin?

Catch basins located on private property are similar to catch basins (also known as storm sewers) that line urban streets to carry away water after rain fall. The lids of these catch basins are metal and have grates.

Can I apply larvicides to catch basins located on my property?

No. Homeowners and owners of properties such as condominium and apartment complexes, parking lots, shopping malls, schools, commercial and industrial properties, golf courses, etc., cannot apply larvicides to catch basins located on their property.

Who can apply larvicides to catch basins on my property?

A larvicide can only be applied into a catch basin by a licensed exterminator or a technician working for a pest control company. The pest control company must obtain the following approvals in order to apply larvicide into catch basins on the property:

• a permit issued by a Ministry of the Environment regional office,
• a letter of approval to carry out larviciding programs from the local Medical Officer of Health, and
• the approval of the local municipality that owns the storm sewer system.

The licensed exterminator will be required as a condition of the permit to give public notice of the use of the larvicide.

What are my options for applying larvicides to stagnant water on my property?

Stagnant water includes water in rain gutters, discarded tires, ornamental ponds, puddles, rain barrels, flood water pools and roadside ditches (if the property owner is responsible for the ditch and it has no flowing water). Preferably, it is best to empty stagnant water from containers on a weekly basis. It the container or stagnant water body cannot be emptied or drained then larviciding may be an option.

There are three options for applying larvicides to wholly contained stagnant water with no outflow located on your property:

1. If you are a homeowner, you can purchase a domestic larvicide product containing either Bti (Bacillus thuringiensis israelensis) or methoprene that is available at MOE-licensed vendor outlets such as hardware stores and garden centres.  Property owners, tenants or their full-time employees do not need a permit and licence or to give public notification to use these products. As a courtesy you may wish to post public signs every 100 metres around the perimeter of the treated water body. These products can be applied only in water that is wholly contained on the property and has no outflow (this would exclude catch basins or flowing ditches). All label directions and precautions must be followed in applying the larvicide.

2. You can hire a pest control company that offers mosquito control services for West Nile Virus to treat stagnant water. This company must obtain a permit issued by a Ministry of the Environment regional office, a letter of approval from the local Medical Officer of Health and provide public notice of larvicide use.

3. If you are a property owner, tenant or the full-time employee of the owner or tenant, you can obtain a Mosquito/Biting Flies licence (contact Ridgetown College-University of Guelph 1-888-620-9999). As a licence holder, you can purchase larvicides available only to those holding the licence and apply them to water that has no outflow from the property (this excludes catch basins). In this case, you are not required to obtain a permit issued by the MOE or provide public notification but you may wish to post signs as described above. 

For further information visit the Ministry of the Environment’s web site at ontario.ca/environment or contact:

Public Information Centre
Ministry of the Environment
135 St. Clair Avenue West
Toronto, ON M4V 1P5
Tel: 416-325-4000 or
1-800-565-4923

Information on West Nile Virus is also available on the Ministry of Health and Long-Term Care's Web site at www.health.gov.on.ca or by calling the toll-free MOHLTC West Nile Virus INFOline at 1-877-234-4343.

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